Below are some of the major players in the backlash over theIRS paying extra attention to advocacy groups whose namesincluded terms such as "patriot" or "Tea Party" when consideringapplications for tax-exempt status.

* Steven Miller - The acting head of the Internal RevenueService while the scandal unfolded. He was fired from the poston Wednesday after an internal IRS report found that poormanagement, and not partisan politics, led to an "inappropriate"focus on conservative groups starting in 2010. The IRS hasacknowledged Miller knew about the targeting of conservativegroups in 2012 but did not disclose the practice. He was theformer deputy IRS commissioner for services and enforcement andhad been at the agency for more than 25 years.

At a House of Representatives hearing on Friday, Millerapologized for "foolish mistakes" made at the IRS and said theyresulted from a heavy workload. He leaves the agency inJune.

* Douglas Shulman - IRS commissioner before Miller took overin the acting capacity in November 2012. A Democrat, he wasappointed to the post under Republican President George W. Bushin 2008.

In March 2012, Shulman told lawmakers that IRS personnelapplied no extra scrutiny to conservative groups, although thenew report from the Treasury Inspector General for TaxAdministration (TIGTA) said that Miller knew of the targeting asearly as March 8, 2012.

Congressional leaders sent letters to Shulman inquiringabout IRS targeting as early as June 2011. According to theinspector general, the IRS's Determinations Unit began targetingconservative groups in March or April of 2010.

* Danny Werfel - the White House budget official selected byObama to replace Miller as acting IRS chief on May 22.

The Obama administration's point man in overseeing the"sequestration" budget cuts, he will now tackle the IRS scandal.

* Lois Lerner - director of the IRS's tax-exempt divisionwho broke the news of the scandal on May 10 at an American BarAssociation function when she publicly apologized for thediscriminatory practices. The admission came just days after shetestified in Congress but did not mention it. According to the inspector general, Lerner learned about thetargeting as early as June 29, 2011.

Lawmakers have called for her removal from the IRS.

Miller on Friday acknowledged that the scandal-exposingquestion-and-answer session had been planned.

* Joseph Grant - IRS acting commissioner of taxexempt/government entities division at the center of thescandal. On Thursday he announced plans to retire on June 3after joining the IRS in 2005. He took over the reins of the taxexempt division in late 2010 and Lerner worked under him.

* Sarah Hall Ingram - Preceded Grant as head of the IRS'stax-exempt division when the targeting of conservative groupsbegan. Since December 2010, she has headed up the IRS divisionhandling Obama administration's healthcare reform.

* William Wilkins - IRS chief counsel who is an Obamapolitical appointee. He is the top legal adviser and takes thelead on all litigation involving the IRS. His office, althoughnot necessarily Wilkins personally, knew of the targeting asearly as August 2011, according to TIGTA. The IRS said Wilkinsdid not participate in the August 2011 meeting, which the agencysaid involved "staff attorneys several layers below Wilkins."

* J. Russell George - Treasury Department inspector generalfor tax administration. Investigated the complaints against theIRS and issued the public report on targeting of conservativegroups. The IRS is an arm of the Treasury Department andlawmakers at the hearings are scrutinizing George for notissuing warnings about the practice earlier.

* IRS's Cincinnati field office employees - oversaw thereviews of tax-exempt applications. According to TIGTA, the Ohiounit set its own criteria for checking tax-exempt groups in theabsence of clear guidance from more senior officials.

Republican lawmakers have named five workers they hope tobring in for questioning: Holly Paz, Washington-based directorof rulings and agreements for the tax exempt division; GregMuthert, a veteran Cincinnati office worker; Joseph Herr andElizabeth Hofacre, who were cited by some Tea Party groups ashandling their tax-exempt applications; and John Shafer, whomlawmakers described as "screening group manager."

A congressional aide said the five workers were chosenbased on a timeline from the TIGTA report that listed the jobroles involved in the activity. It was unclear whether theseemployees had any role in any wrongdoing.